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modifyVerifier (Modification Verifier)
This element specifies the write protection settings which have been applied to a PresentationML document.
Write protection refers to a mode in which the document's contents cannot be modified, and the document
cannot be resaved using the same file name.
When present, the application shall require a password to enable modifications to the document. If the
supplied password does not match the hash value in this attribute, then write protection shall be enabled. If this
element is omitted, then no write protection shall be applied to the current document. Since this protection
does not encrypt the document, malicious applications may circumvent its use.
The password supplied to the algorithm is to be a Unicode string; strings longer than 255 characters are
truncated to 255 characters. The attributes of this element specify the algorithm to be used to verify the
password provided by the user.
[Example: Consider a PresentationML document that can only be opened in a write protected state unless a
password is provided, in which case the file would be opened in an editable state. This requirement would be
specified using the following PresentationML:
<p:documentProtection …
p:cryptAlgorithmClass="hash" p:cryptAlgorithmType="typeAny"
p:cryptAlgorithmSid="1" p:hashData="9oN7nWkCAyEZib1RomSJTjmPpCY=" ... />
In order for the hosting application to enable edits to the document, the hosting application would have to be
provided with a password that the hosting application would then hash using the algorithm specified by the
algorithm attributes and compare to the value of the hashData attribute (9oN7nWkCAyEZib1RomSJTjmPpCY=).
If the two values matched, the file would be opened in an editable state. end example]
Parent Elements
presentation (§Error! Reference source not found.)
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Attributes
algIdExt
(Cryptographic
Algorithm
Extensibility)
Description
Specifies that a cryptographic algorithm which was not defined by this Office Open XML
Standard has been used to generate the hash value stored with this document.
This value, when present, shall be interpreted based on the value of the algIdExtSource
attribute in order to determine the algorithm used, which shall be application-defined.
[Rationale: This extensibility affords the fact that with exponentially increasing
computing power, documents created in the future will likely need to utilize as yet
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Attributes
Description
undefined hashing algorithms in order to remain secure. end rationale]
If this value is present, the cryptAlgorithmClass, cryptAlgorithmType, and
cryptAlgorithmSid attribute values shall be ignored in favor of the algorithm defined by
this attribute.
[Example: Consider a PresentationML document with the following information stored in
its protection element:
<p:… p:algIdExt="0000000A"
p:algIdExtSource="futureCryptography"
p:hashData="9oN7nWkCAyEZib1RomSJTjmPpCY=" />
The algIdExt attribute value of 0000000A specifies that the algorithm with hex code A
shall be used as defined by the futureCryptography application. end example]
The possible values for this attribute are defined by the XML Schema unsignedInt
datatype.
algIdExtSource
(Algorithm
Extensibility Source)
Specifies the application which defined the algorithm value specified by the algIdExt
attribute.
[Example: Consider a PresentationML document with the following information stored in
one its protection element:
<p:… p:algIdExt="0000000A"
p:algIdExtSource="futureCryptography"
p:hashData="9oN7nWkCAyEZib1RomSJTjmPpCY=" />
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Attributes
Description
The algIdExtSource attribute value of futureCryptography specifies that the algorithm
used here was published by the futureCryptography application. end example]
The possible values for this attribute are defined by the XML Schema string datatype.
cryptAlgorithmClass
(Cryptographic
Algorithm Class)
Specifies the class of cryptographic algorithm used by this protection. [Note: The initial
version of this Office Open XML Standard only supports a single version - hash - but
future versions may expand this as necessary. end note]
[Example: Consider a PresentationML document with the following information stored in
its protection element:
<p:… p:cryptAlgorithmClass="hash"
p:cryptAlgorithmType="typeAny"
p:cryptAlgorithmSid="1"
p:hashData="9oN7nWkCAyEZib1RomSJTjmPpCY=" />
The cryptAlgorithmClass attribute value of hash specifies that the algorithm used for the
password is a hashing algorithm. end example]
The possible values for this attribute are defined by the ST_AlgClass simple type (§Error!
Reference source not found.).
cryptAlgorithmSid
(Cryptographic
Hashing Algorithm)
Specifies the specific cryptographic hashing algorithm which shall be used along with the
saltData attribute and user-supplied password in order to compute a hash value for
comparison.
The possible values for this attribute shall be interpreted as follows:
Value
Algorithm
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Attributes
Description
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MD2
2
MD4
3
MD5
4
SHA-1
5
MAC
6
RIPEMD
7
RIPEMD-160
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Undefined. Shall not be used.
9
HMAC
10
Undefined. Shall not be used.
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Undefined. Shall not be used.
12
SHA-256
13
SHA-384
14
SHA-512
Any other
value
Undefined. Shall not be used.
[Example: Consider a PresentationML document with the following information stored in
its protection element:
<p:… p:cryptAlgorithmClass="hash"
p:cryptAlgorithmType="typeAny"
p:cryptAlgorithmSid="1"
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Attributes
Description
p:hashData="9oN7nWkCAyEZib1RomSJTjmPpCY=" />
The cryptAlgorithmSid attribute value of 1 specifies that the SHA-1 hashing algorithm
shall be used to generate a hash from the user-defined password. end example]
The possible values for this attribute are defined by the XML Schema unsignedInt
datatype.
cryptAlgorithmType
(Cryptographic
Algorithm Type)
Specifies the type of cryptographic algorithm used by this protection. [Note: The initial
version of this Office Open XML Standard only supports a single type - typeAny - but
future versions may expand this as necessary. end note]
[Example: Consider a PresentationML document with the following information stored in
its protection element:
<p:… p:cryptAlgorithmClass="hash"
p:cryptAlgorithmType="typeAny"
p:cryptAlgorithmSid="1"
p:hashData="9oN7nWkCAyEZib1RomSJTjmPpCY=" />
The cryptAlgorithmType attribute value of typeAny specifies that any type of algorithm
may have been used for the password. end example]
The possible values for this attribute are defined by the ST_AlgType simple type (§Error!
Reference source not found.).
cryptProvider
(Cryptographic
Provider)
Specifies the cryptographic provider which was used to generate the hash value stored in
this document. If the user provided a cryptographic provider which was not the system's
built-in provider, then that provider shall be stored here so it can subsequently be used if
available.
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Attributes
Description
If this attribute is omitted, then the built-in cryptographic provider on the system shall be
used.
[Example: Consider a PresentationML document with the following information stored in
its protection element:
<p:… p:cryptProvider="Krista'sProvider"
p:hashData="9oN7nWkCAyEZib1RomSJTjmPpCY=" />
The cryptProvider attribute value of Krista'sProvider specifies that the cryptographic
provider with name "Krista's Provider" shall be used if available. end example]
The possible values for this attribute are defined by the XML Schema string datatype.
cryptProviderType
(Cryptographic
Provider Type)
Specifies the type of cryptographic provider to be used.
[Example: Consider a PresentationML document with the following information stored in
its protection element:
<p:… p:cryptProviderType="rsaAES"
p:hashData="9oN7nWkCAyEZib1RomSJTjmPpCY=" />
The cryptProviderType attribute value of rsaAES specifies that the cryptographic provider
type shall be an Advanced Encryption Standard provider. end example]
The possible values for this attribute are defined by the ST_CryptProv simple type
(§Error! Reference source not found.).
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Attributes
cryptProviderTypeE
xt (Cryptographic
Provider Type
Extensibility)
Description
Specifies that a cryptographic provider type which was not defined by this Office Open
XML Standard has been used to generate the hash value stored with this document.
This value, when present, shall be interpreted based on the value of the
cryptProviderTypeExtSource attribute in order to determine the provider type used,
which shall be application-defined. [Rationale: This extensibility affords the fact that with
exponentially increasing computing power, documents created in the future will likely
need to utilize as yet undefined cryptographic provider types in order to remain secure.
end rationale]
If this value is present, the cryptProviderType attribute value shall be ignored in favor of
the provider type defined by this attribute.
[Example: Consider a PresentationML document with the following information stored in
its protection element:
<p:… p:cryptProviderTypeExt="00A5691D"
p:cryptProvideTypeExtSource="futureCryptography"
p:hashData="9oN7nWkCAyEZib1RomSJTjmPpCY=" />
The cryptProviderTypeExt attribute value of 00A5691D specifies that the provider type
associated with hex code A5691D shall be used as defined by the futureCryptography
application. end example]
The possible values for this attribute are defined by the XML Schema unsignedInt
datatype.
cryptProviderTypeE
xtSource (Provider
Type Extensibility
Source)
Specifies the application which defined the provider type value specified by the
cryptProviderTypeExt attribute.
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Attributes
Description
[Example: Consider a PresentationML document with the following information stored in
its protection element:
<p:… p:cryptProviderTypeExt="00A5691D"
p:cryptProvideTypeExtSource="futureCryptography"
p:hashData="9oN7nWkCAyEZib1RomSJTjmPpCY=" />
The cryptProvideTypeExtSource attribute value of futureCryptography specifies that the
provider type used here was published by the futureCryptography application. end
example]
The possible values for this attribute are defined by the XML Schema string datatype.
hashData (Password
Hash)
Specifies the hash value for the password stored with this document. This value shall be
compared with the resulting hash value after hashing the user-supplied password using
the algorithm specified by the preceding attributes and parent XML element, and if the
two values match, the protection shall no longer be enforced.
If this value is omitted, then no password shall be associated with the protection, and it
may be turned off without supplying any password.
[Example: Consider a PresentationML document with the following information stored in
its protection element:
<p:… p:cryptAlgorithmClass="hash"
p:cryptAlgorithmType="typeAny"
p:cryptAlgorithmSid="1"
p:hashData="9oN7nWkCAyEZib1RomSJTjmPpCY=" />
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Attributes
Description
The hashData attribute value of 9oN7nWkCAyEZib1RomSJTjmPpCY= specifies that the
user-supplied password shall be hashed using the pre-processing defined by the parent
element (if any) followed by the SHA-1 algorithm (specified via the cryptAlgorithmSid
attribute value of 1) and that the resulting has value must be
9oN7nWkCAyEZib1RomSJTjmPpCY= for the protection to be disabled. end example]
The possible values for this attribute are defined by the XML Schema string datatype.
saltData (Salt for
Password Verifier)
Specifies the salt which was prepended to the user-supplied password before it was
hashed using the hashing algorithm defined by the preceding attribute values to generate
the hashData attribute, and which shall also be prepended to the user-supplied password
before attempting to generate a hash value for comparison. A salt is a random string
which is added to a user-supplied password before it is hashed in order to prevent a
malicious party from pre-calculating all possible password/hash combinations and simply
using those precalculated values (often referred to as a "dictionary attack").
If this attribute is omitted, then no salt shall be prepended to the user-supplied password
before it is hashed for comparison with the stored hash value.
[Example: Consider a PresentationML document with the following information stored in
its protection element:
<p:… p:saltData="ZUdHa+D8F/OAKP3I7ssUnQ=="
p:hashData="9oN7nWkCAyEZib1RomSJTjmPpCY=" />
The saltData attribute value of ZUdHa+D8F/OAKP3I7ssUnQ== specifies that the usersupplied password shall have this value prepended before it is run through the specified
hashing algorithm to generate a resulting hash value for comparison. end example]
The possible values for this attribute are defined by the XML Schema string datatype.
spinCount
Specifies the number of times the hashing function shall be iteratively run (using each
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Attributes
Description
(Iterations to Run
Hashing Algorithm)
iteration's result as the input for the next iteration) when attempting to compare a usersupplied password with the value stored in the hashData attribute. [Rationale: Running
the algorithm many times increases the cost of exhaustive search attacks
correspondingly. Storing this value allows for the number of iterations to be increased
over time to accommodate faster hardware (and hence the ability to run more iterations
in less time). end rationale]
[Example: Consider a PresentationML document with the following information stored in
its protection element:
<p:… p:spinCount="100000"
p:hashData="9oN7nWkCAyEZib1RomSJTjmPpCY=" />
The spinCount attribute value of 100000 specifies that the hashing function shall be run
one hundred thousand times to generate a hash value for comparison with the hash
attribute. end example]
The possible values for this attribute are defined by the XML Schema unsignedInt
datatype.
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The following XML Schema fragment defines the contents of this element:
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<complexType name="CT_ModifyVerifier">
<attribute name="cryptProviderType" type="ST_CryptProv" use="required"/>
<attribute name="cryptAlgorithmClass" type="ST_AlgClass" use="required"/>
<attribute name="cryptAlgorithmType" type="ST_AlgType" use="required"/>
<attribute name="cryptAlgorithmSid" type="xsd:unsignedInt" use="required"/>
<attribute name="spinCount" type="xsd:unsignedInt" use="required"/>
<attribute name="saltData" type="xsd:string" use="required"/>
<attribute name="hashData" type="xsd:string" use="required"/>
<attribute name="cryptProvider" type="xsd:string" use="optional"/>
<attribute name="algIdExt" type="xsd:unsignedInt" use="optional"/>
<attribute name="algIdExtSource" type="xsd:string" use="optional"/>
<attribute name="cryptProviderTypeExt" type="xsd:unsignedInt" use="optional"/>
<attribute name="cryptProviderTypeExtSource" type="xsd:string" use="optional"/>
</complexType>
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